**Core Concept**
Ovarian serous cystadenocarcinoma is a type of epithelial ovarian cancer, which is the most common type of ovarian cancer. The management of ovarian cancer involves a multidisciplinary approach, including surgery, chemotherapy, and targeted therapy.

**Why the Correct Answer is Right**
The next step in the management of ovarian serous cystadenocarcinoma after initial surgery is to assess the patient's risk category using the FIGO (International Federation of Gynecology and Obstetrics) staging system. Based on the risk category, the patient will be started on adjuvant chemotherapy. The standard chemotherapy regimen for ovarian cancer is a combination of carboplatin and paclitaxel. This regimen has been shown to improve survival rates in patients with ovarian cancer.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not address the need for adjuvant chemotherapy in ovarian cancer. While surgery is an essential component of ovarian cancer management, it is not sufficient as a standalone treatment for most patients.

**Option B:** This option is incorrect because it does not take into account the patient's risk category or the need for adjuvant chemotherapy. While hormone replacement therapy may be considered for patients with ovarian cancer, it is not the next step in management after initial surgery.

**Option C:** This option is incorrect because it does not address the need for adjuvant chemotherapy in ovarian cancer. While targeted therapy may be considered for patients with specific genetic mutations, it is not the next step in management after initial surgery.

**Clinical Pearl / High-Yield Fact**
It is essential to assess the patient's risk category using the FIGO staging system to determine the appropriate next step in management. The FIGO staging system takes into account the extent of disease spread and helps guide treatment decisions.

**Correct Answer: C.** Chemotherapy with carboplatin and paclitaxel is the next step in the management of ovarian serous cystadenocarcinoma after initial surgery.